Horizontal shareholding exists when significant shareholders have stock in horizontal competitors. (It is often imprecisely called "common shareholding," but that term can also apply when shareholders own stock in two noncompeting corporations. It differs from "cross-shareholding," which...

This Article shows that new economic proofs and empirical evidence provide powerful confirmation that, even when horizontal shareholders individually have minority stakes, horizontal shareholding in concentrated markets often has anticompetitive effects. The new economic proofs show that,...